1891. | SEELYE—ON INDIGENOUS FERNS. 189 
these facts in mind we can satisfactorily account for the paucity of the 
plant in our own vicinity, which, though not lacking an atmosphere 
comparatively moist, yet has few localities well sheltered from the sun 
whose fervent summer rays are felt fora long term ; where favorable 
spots exist here, close to a body of water, the common Polypody is 
sometimes found. 
Shirley Hibbard, an English horticulturist, remarks in relation 
to this plant : *“‘ None of our native ferns endure drought so well as 
this.”” In view of what has been written above, this statement would 
seem at least doubtful to one not well acquainted with the habits of 
the plant. Yet it is true that when once established it will persist 
in localities which are apparently very unpropitious, such as on the 
brink of cliffs, nestled beneath the exposed root of some tree or shrub 
and where all about, outside of shade, the sun for half the day strikes 
with great power. In such places the fronds for many days in 
summer will partially roll up and wither and seem to be dying, but with 
the return of the cooler season and plentiful rains, will straighten out 
and resume a normal appearance. In these circumstances, however, 
the plants never exhibit exuberant growth. When the plant has 
become established in a spot where its existence is something of a 
struggle it is enabled to endure a long season of drought by means of 
the nutriment stored up in its somewhat fleshy rhizome. The mode of 
root growth of Polypodium vulgare, is the cause of its shrinking from 
the sun in unfavorable locations. It sends down no strong roots, but 
from the rhizome spread out laterally some rootlets, almost hair-like, 
into the light vegetable mould on the surface or in the crevices of rocks 
from which alone it gathers its nourishment. As has been noticed in 
the case of the Oxoclea, which can stand a full exposure to the sun 
when its roots are constantly supplied with moisture, so this Polypody 
when surrounded by conditions which enable it easily to conserve its 
moisture can bear the full sunshine on the face of a rock. One other 
example in illustration of the same point may be given. <Asprdium 
marginale, Swartz, in this region, grows only in the shade, but in the 
Canadian locality which has been mentioned, it grows freely in the 
open fields, and next to the common Polybody is the fern most 
frequently found in that region. Both Gray and Eaton give the habitat 
of this fern as “rocky hillsides in rich woods,” and the definition is 
correct for most parts Of the United States ; in the Dominion of Canada, 
however, it is different, and it was a pleasure to have my own observa- 
tion on this point confirmed by Dr. Lawson, of Dalhousie University, 
when a copy of his tFern Flora of Canada was received last year. In 
* Shirley Hibbard, The Fern Garden, 4th Ed., p. 84. 
+ Lawson, Fern Flora of Canada, p. 242. 
